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Nait 3 Balance control

Discussion in 'd.i.y.' started by istari_knight, Oct 15, 2014.

  1. istari_knight

    istari_knight pfm Member

    Just picked up a Nait 3 sans balance control, there are just 6 "stumps" where it used to be... No idea how it was done but someone's ripped it off the board :mad:

    Looking at internal pictures on the net it appears the original was marked "10KD" - "10KRD" ... Any idea what that is ? Google thinks it may mean antilog but best to ask here before buying/fitting the wrong one.
     
  2. nickcase

    nickcase Enlightened Member

    Do you need a balance control? i.e. do you need to compensate for listening room topography?

    If not then use a pair of decent matched resistors (1K2 would do) and link the signal pads on the PCB.

    Will sound better than a crappy balance pot sat in the signal path.

    Nick
     
  3. istari_knight

    istari_knight pfm Member

    Thanks for the tip Nick. Ideally I'd like to keep it 100% original & the balance control is quite handy when one speaker is further than the other from the listening chair :)
     
  4. colasblue

    colasblue pfm Member

    Recently been there with a Naim 82.

    Bottom line is its a special 10K log pot with the tapers running in opposite directions, and it seems you can't get one anywhere these days!

    My solution was to substitute a 10K linear pot with two 470R shunt resistors to give similarish performance. It works well. A 20K linear pot with about 1k as a shunt would have been closer electrically but Alps don't make a 20K linear. I presume it is an alps blue pot that's required?
     
  5. istari_knight

    istari_knight pfm Member

    I feared as much ! Okay so what you're describing appears to be the same as Fig.9 here: http://sound.westhost.com/pots.htm

    You've tried it & found it to work so I'll follow suit :D
     
  6. colasblue

    colasblue pfm Member

    yes- that's it

    I chose the values to keep the proportion of signal tapped about the same as with the original pot at centre position.
     
  7. istari_knight

    istari_knight pfm Member

    Thanks for that, parts now on order... I'll let you know how it goes.
     
  8. nickcase

    nickcase Enlightened Member

    Splendid :)

    If the balance pot was missing might there be other mods or alterations?
     
  9. istari_knight

    istari_knight pfm Member

    Thankfully it's completely untouched. Looking at the "stumps" the balance pot wasn't removed more like snapped off, in fact half of it is still attached to the plastic extension shaft... Very odd !
     
  10. nickcase

    nickcase Enlightened Member

    Odd indeed, that's some rough handling!

    Can you rescue the extension shaft?
     
  11. istari_knight

    istari_knight pfm Member

    The knob/extension shaft are intact... I can only guess someone has pulled the balance knob really hard tearing the balance pot apart - Goodness knows how/why :confused:

    Parts are due tomorrow so I'll post a picture up to show what I mean before I fit the new one.
     
  12. juz400

    juz400 pfm Member

    Appologies for being late to the party, I dont think the balance pot is an alps blue, the volume pot is though!
     
  13. istari_knight

    istari_knight pfm Member

    Indeed, the volume pot is an Alps Blue whilst the balance pot is a bog-standard jobbie [Still Alps though I think.]

    All sorted now, fitted a 10K linear pot with 560R shunt resistors [all i had close enough !] It works perfectly... Indistinguishable from a proper balance pot in fact :)

    Cheers for that.
     
  14. istari_knight

    istari_knight pfm Member

    Unmolested:

    [​IMG]

    The stumps:

    [​IMG]

    And singing again [shunt R's on underside of PCB]:

    [​IMG]
     
  15. istari_knight

    istari_knight pfm Member

  16. Chops54

    Chops54 pfm Member


    The balance pot is a potential divider so there should also be a pair of 7.8K resistors?
     
  17. colasblue

    colasblue pfm Member

    I had a look at that Familygate pot when I was servicing my 82. It actually isn't quite the same as a 10KRD since it has no resistance on either side at top dead centre. Hence installing it would slightly increase the gain on a Naim pre and it wouldn't work quite the same in that the correct thing turns one side up at the same time as it turns the other side down. The Familygate special just turns one side or the other down I suspect.

    I think with a bit of fiddling it would be possible to motorise it.
     

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